1. Field of the Invention
The present invention relates to a display panel, in particular, a display panel including an inspection circuit for detecting defects.
2. Description of the Related Art
A liquid crystal display panel using thin-film transistors is known as a display panel and is widely used for a television set, a personal-computer display, a cellular phone, and the like.
The liquid crystal display panel generally includes: a display region in which a plurality of pixels are formed; and a peripheral region surrounding the display region. In recent years, with an increase in area of the display region, the peripheral region is reduced. Accordingly, it becomes difficult to ensure a space for providing inspection terminals in the peripheral region. The inspection terminals are provided to turn the liquid crystal display panel ON for inspection of the liquid crystal display panel. Therefore, as a method for detecting a defect of the liquid crystal display panel, a pseudo dynamic lighting inspection (hereinafter, referred to as “QD lighting inspection”) is used (see JP 2004-101863 A and JP 2001-324721 A). According to the QD lighting inspection, the number of inspection terminals can be reduced by providing an inspection circuit to the liquid crystal display panel.
FIG. 9 is a schematic diagram of a display panel in the related art. A driver for driving liquid crystal (hereinafter, referred to simply as “driver”) provided to the display panel does not have an RGB switching function. A part of a circuit other than drain lines is omitted in FIG. 9.
As illustrated in FIG. 9, a display panel 900 includes a pixel region section 903 and a driver region section 980. In the pixel region section 903, a pixel region 901 and inspection transistors 902 are provided. In the driver region section 980, a driver installation region 904 in which a driver is provided, an R drain-line inspection terminal 905, a G drain-line inspection terminal 906, and a B drain-line inspection terminal 907 are provided.
The inspection transistors 902 are provided in an area of the pixel area section 903, which is situated on the opposite side to the driver installation region 904 as viewed from the pixel region 901. The inspection transistors 902 are respectively provided so as to correspond to R-pixels, G-pixels, and B-pixels provided in the pixel region 901. Drains of the inspection transistors 902 are connected to an R inspection wiring 908, a G inspection wiring 909, and a B inspection wiring 910 according to RGB of the pixels in the pixel region 901. Further, the R inspection wiring 908, the G inspection wiring 909, and the B inspection wiring 910 are respectively connected to the R drain-line inspection terminal 905, the G drain-line inspection terminal 906, and the B drain-line inspection terminal 907 provided in the driver region section 980. A gate of each of the inspection transistors 902 is connected to a gate line terminal 912 provided in the driver region section 980 through an intermediation of a gate wiring 911. A wiring from a source of each of the inspection transistors 902 passes through the pixel region 901 to be provided in the driver installation region 904.
In this case, there is a problem that breaking or short-circuiting cannot be detected for the wirings provided in an area from the driver installation region 904 to the pixel region 901.
Therefore, in the case where the driver has the RGB switching function, a configuration in which an inspection circuit is provided in the driver installation region is known as illustrated in FIG. 10. In FIG. 10, a part of the circuit other than the drain lines is omitted.
As illustrated in FIG. 10, a display panel 960 includes RGB switches 920 provided in an area of the pixel region section 903, which is situated between the driver installation region 904 in which the driver is provided and the pixel region 901. RGB-switch terminals 921, 922, and 923 are provided in the driver region section 980.
A source of each of the RGB switches 920 is connected to one of the R-, G-, and B-pixels provided in the pixel region 901. Gates of the RGB switches 920 are connected to the RGB-switch terminals 921, 922, and 923 through an intermediation of RGB-switch gate wirings 971, 972, and 973, for a corresponding one of the R-, G-, and B-pixels provided in the pixel region 901. After the RGB switches 920, each including three transistors, are connected in parallel to each other, a drain of the RGB switches 920 is connected to a source of each of the inspection transistors 930 by a wiring. Further, a drain-line inspection terminal 941 is connected to a drain of each of the inspection transistors 930 through an intermediation of a drain-line inspection wiring 940, whereas a gate line terminal 951 is connected to a gate of each of the inspection transistors 930 through an intermediation of a gate wiring 950.
In comparison with the case illustrated in FIG. 9, switching can be performed by the RGB switches 920 to conduct the QD lighting inspection in this case. Therefore, the number of the inspection transistors 930 can be reduced to one-third, which allows a large area to be ensured for the inspection circuit including the inspection transistors 930. As a result, even if output terminals of the driver become extremely fine, a desired width of each of the inspection transistors can be ensured. Moreover, the breaking or the short-circuiting of the wiring from each of the output terminals of the driver to the pixel region can be detected.